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ABSTRACT: Miconazole at 10 mg/l effected rapid (less than 1 min) and substantial (greater than 99%) reductions of intracellular ATP concentrations in buffered suspensions of Candida albicans. This ATP-suppressive effect was mirrored by a rapid reduction in the viable counts of the suspensions. However, the presence of exogenous glucose or fructose (but not several other carbon sources) greatly retarded the ATP-suppressive effect of miconazole. Glucose and fructose could even reverse the suppression when they were added to miconazole-pretreated suspensions. These data indicated that the non-viable cells remained metabolically active. The abrogatory effect of glucose on ATP reduction was optimal between pH 6.5 and 7: it was prevented by fluoride, a known inhibitor of glycolysis, and 2-deoxy-D-glucose could not substitute for glucose, demonstrating that metabolism of glucose was essential for the effect. Two detergents and orthovanadate were much less potent ATP suppressors than miconazole, but the proton pump uncoupler, carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) was 10 times more active. The results suggest that miconazole may reduce ATP either by uncoupling substrate uptake mechanisms dependent on the fungal membrane proton pump or by inhibition of plasma membrane ATPase.
Journal of Antimicrobial Chemotherapy 01/1990; 24(6):905-19. · 5.07 Impact Factor
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ABSTRACT: Fluconazole is a novel triazole antifungal intended for oral treatment of superficial and systemic mycoses. In tests done in standard mycological media, the compound had minimal inhibitory concentrations against pathogenic Candida species that were usually in excess of 100 mg/l. By contrast, its 'relative inhibition factors' against Candida species (calculated from areas under the antifungal dose-response curves) were of the same order as those of other imidazole and triazole antifungal agents. Against pathogenic Aspergillus species and dermatophytes, the mean relative inhibition factors were the highest so far recorded for an azole antifungal, indicating a relatively weak inhibitory activity against these fungi. Fluconazole inhibited branching and hyphal development in C. albicans at concentrations as low as 10(-6) M (0.3 mg/l), but miconazole and ketoconazole were still active in these tests at concentrations 100 times lower than this. The new antifungal did not suppress ATP concentrations in C. albicans spheroplasts, in common with other weakly lipophilic azole antifungals. This overall poor activity of fluconazole in vitro corresponds badly with its high activity in animal models of mycoses in vivo, and provides more evidence for the unreliability of tests with azole antifungals in vitro as predictors of potential efficacy in vivo.
Journal of Antimicrobial Chemotherapy 11/1986; 18(4):473-8. · 5.07 Impact Factor
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ABSTRACT: Low, reproducible minimal inhibitory concentrations against Candida species, with sharp, precise end points in complex media were achieved for imidazoles (clotrimazole, econazole, miconazole, tioconazole and ketoconazole) and triazoles (fluconazole, itraconazole, vibunazole, ICI 153066) by including in the test medium antibacterial antibiotics that bind to the 80S eukaryotic ribosome and inhibit protein synthesis, i.e. blasticidin, cycloheximide, doxycycline, neomycin and gentamicin. The presence of these antibiotics reduced MICs, on average, by 50- to 250-fold. Other protein synthesis inhibitors (rifampicin, erythromycin, lincomycin, clindamycin, chloramphenicol and fusidic acid) were not effective, and the antibiotics did not affect MICs for Aspergillus species. The low azole MICs were in close agreement with MICs obtained in a defined, tissue culture-based medium lacking added antibiotics.
Journal of medical and veterinary mycology: bi-monthly publication of the International Society for Human and Animal Mycology 09/1986; 24(4):305-11.
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ABSTRACT: Several antifungal agents, at concentrations of 10 micrograms/ml, were shown to suppress ATP concentrations very rapidly in intact cells and spheroplasts of Candida albicans. The highest ATP-suppressing activity was shown by the highly lipophilic imidazole derivatives difonazole, clotrimazole, econazole, isoconazole, miconazole, oxiconazole and tioconazole, which all caused a reduction of cellular ATP content of more than 50% in 10 min. Relatively hydrophilic imidazole derivatives such as ketoconazole were essentially inactive in the test, as were the triazole derivatives fluconazole, ICI 153066, itraconazole and terconazole, and 5-fluorocytosine. Amphotericin B and terbinafine possessed intermediate ATP-suppressing activity, and the dose-response and pH-response curves for these compounds suggested their mechanism of ATP suppression differed from that of the active imidazole derivatives. ATP suppression by azole antifungals did not involve leakage of ATP from the cells and the effect was entirely abrogated by the presence of serum. Intact cells and spheroplasts of yeast-form and hyphal-form C. albicans were generally equally sensitive to ATP suppression, but stationary-phase cells of both morphological forms were less sensitive than exponential-phase cells. The extent of ATP suppression was significantly reduced in stationary-phase yeast cells of a C. albicans strain with known resistance to azole antifungals, but exponential-phase cells of resistant and susceptible strains were equally sensitive. The effect is tentatively ascribed to membrane damage caused directly by the antifungals.
Sabouraudia 01/1986; 23(6):415-24.
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ABSTRACT: Six azole-derivative antifungal compounds affected several aspects of Candida albicans hyphal development with only a relatively small degree of inhibition of growth rate, measured in terms of ATP concentration, whereas amphotericin B and 5-fluorocytosine affected morphology only when they also substantially inhibited fungal growth rate. At 10(-8) M, all the azoles tested inhibited branch formation by C. albicans hyphae. At 10(-7) M and higher concentrations, clotrimazole and miconazole strongly suppressed emergence of new hyphal outgrowths from parent yeast cells, whereas ICI 153066 and itraconazole had little effect on this phenomenon and ketoconazole and tioconazole had intermediate effects. At the highest concentrations tested (10(-5) M) hyphal development was ultimately arrested by the azole compounds and the fungus grew predominantly in the form of budding yeast cells; however, none of the azole antifungals prevented initial emergence of an apparently normal germ tube. The antifungals only exerted their morphological effects when they were present in the culture medium: removal of the compounds after exposure of C. albicans to them led to reversion to normal growth.
Journal of general microbiology 11/1985; 131(10):2581-9.
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ABSTRACT: Nine new antifungal agents were tested for their activity in vitro in terms of relative inhibition factors (RIFs) against 26 isolates of Candida species, eight isolates of Aspergillus species and six isolates of dermatophyte fungi. Eight of the new compounds were azole antifungals, the ninth was a phenylmorpholine derivative. Against Candida species, all the novel compounds gave RIFs that were of a similar order to RIFs for established imidazole compounds. Two topical antifungals, butoconazole and terconazole, and two systemic antifungals, itraconazole and vibunazole, gave mean RIFs less than 60% in tests with Candida species, and therefore matched clotrimazole, ketoconazole and tioconazole in terms of RIF. However, none of the new compounds gave RIFs as low as amphotericin B against the Candida isolates. Against Aspergillus isolates, itraconazole, with a mean RIF of 25%, was even more active in vitro than amphotericin B. Vibunazole was as active as ketoconazole against Aspergillus isolates. All the new antifungals except Bay l-9139 gave very low RIFs against dermatophyte isolates, and thus matched established imidazole antifungals for inhibitory effects in vitro. In terms of RIF data, all the nine new compounds tested appear to offer reasonable potential for antifungal chemotherapy in vivo. A similar conclusion would not have been drawn from minimal inhibitory concentration data, which tended to show most of the new antifungals in a very poor light. Tests with amphotericin B, 5-fluorocytosine and ketoconazole showed that RIF can vary substantially with the pH of the test medium. For amphotericin B and ketoconazole the best activity was seen at neutral pH values; for 5-fluorocytosine the greatest inhibitory activity was found at lower pH values.
Journal of Antimicrobial Chemotherapy 09/1984; 14(2):105-14. · 5.07 Impact Factor
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ABSTRACT: A system is described for measurement of relative inhibition factors (RIFs) for antifungal agents--that is, the area under a fixed portion of the antifungal dose-response curve, expressed as a percentage of the area under the dose-response curve for a theoretical noninhibitory substance. The RIFs for two polyenes, 5-fluorocytosine (5FC) and griseofulvin correlated with the known inhibitory activity of these compounds against pathogenic yeasts, Aspergillus spp. and dermatophytes in vitro and in vivo, but revealed wholly new relative inhibitory properties among five imidazole antifungals: ketoconazole and tioconazole emerged as the most active imidazole antifungals against yeasts and clotrimazole and econazole against Aspergillus spp. Because of the high reproducibility of the assay, and because tests were done in a tissue culture medium in the presence of serum, it is considered that measurement of RIFs could give better predictions of likely antifungal activity in vivo than is at present afforded by tests for minimal inhibitory concentrations.
Journal of Antimicrobial Chemotherapy 02/1984; 13(1):31-43. · 5.07 Impact Factor
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ABSTRACT: Strain phenotypes of 330 Candida albicans isolates from five areas in the United States were determined on the basis of nine biochemical tests. Statistical analysis of the distribution of phenotypes revealed no significant differences among types from different anatomical sources. However, there were some differences among the phenotypes of strains from the different geographical areas, and there were substantial differences in biochemical phenotypes associated with strains susceptible and resistant to 5-fluorocytosine and between strains of serotypes A and B. Geographical differences in phenotypes of C. albicans were also noted between the 330 U.S. isolates and 247 isolates from Britain. Cluster analysis of the U.S. strains alone and of all of the U.S. and U.K. strains showed that C. albicans phenotypes can be grouped into fewer than 20 clusters with common biochemical properties.
Journal of Clinical Microbiology 11/1983; 18(4):849-57. · 4.15 Impact Factor
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ABSTRACT: The strain phenotypes of 266 C. albicans isolates from patients attending a genitourinary clinic were determined on the basis of 9 biochemical tests. Analysis of the strain patterns of isolates from the genitalia showed that there were no statistically significant differences between types associated with clinically overt Candida infection and types isolated in the absence of symptoms of candidosis. This finding accords with the traditional view of C. albicans as an opportunistic pathogen, rather than a species containing some strains of high virulence. In cases where isolations were made from the same patient at different times, or from different anatomical sites in the same patient, it was found that usually, but not always, a patient carried the same phenotype at different sites and different times. Similarly, the same strain type was isolated from the genitalis of both partners in a majority of instances where strains were isolated from consorts; however, this was not the case for a substantial minority of couples, particularly in those where high promiscuity appeared to promote considerable mixture and interchange of the C. albicans genital microflora.
European Journal of Obstetrics & Gynecology and Reproductive Biology 05/1983; 15(1):37-43. · 1.97 Impact Factor
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Sabouraudia 04/1983; 21(1):79-81.
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ABSTRACT: A system of 10 agar plate tests allowed presumptive identification of Candida albicans and differentiation of up to 512 strain types within the species. The yeast isolates were tested for acid and salt tolerance, proteinase production, resistance to 5-fluorocytosine and safranine, and assimilation of urea, sorbose, citrate and glycine. Media were inoculated semiquantitatively with a multiple-pronged device so that 55 yeasts and 5 reference strains could be printed on each plate at once. The results for the 9 strain differentiation tests were arranged in 3 groups to allow simple designation of types by 3-digit numbers. Mouth and vaginal samples from 85 patients and healthy volunteers yielded to 45 different strain types, of which types 153, 157 and 357 were the most prevalent. The reproducibility of the system was good, if attention was paid to the precision which the media were prepared and inoculated. The effect of test variables, including incubation temperature, medium pH and inoculum size, was assessed. Work is presently in progress to extend the system for presumptive identification of other clinically important Candida spp. and differentiation of their strain types.
Sabouraudia 01/1981; 18(4):301-17.
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ABSTRACT: The pH reactions, ultraviolet spectra and phosphorus content of solutions of a variety of commercially available peptones all indicated, predictably, considerable differences in the chemical composition of the peptones. The effects of these differences on the outcome of experiments with Candida albicans grown in different peptone media was investigated. The fungus produced germ tubes equally effectively on all such media provided that the inoculum was kept to 10(6) blastospores/ml or less. However, expression of inducible enzyme activities in C. albicans varied extensively from peptone to peptone; there was, for example, an inverse relationship between the inorganic phosphorus content of peptones and the amount of acid phosphomonoesterase detectable in intact blastospores. The results indicated that use of different peptones in "Sabouraud's" media by different laboratories may account for some, but not all, published instances of irreproducibility of experiments with C. albicans.
Sabouraudia 01/1979; 16(4):237-46.
